Battling Drug-Resistant HIV Strains in Newly Infected Patients

Nov. 16, 1999 (Atlanta) -- Swiss researchers are shedding some light on an emerging concern: drug-resistant strains of HIV -- the virus that causes AIDS -- in recently infected patients. Some types of HIV are showing resistance to protease inhibitors -- among the most effective anti-HIV drugs. The researchers' findings are published in a recent issue of The Lancet.

Highly active antiretroviral therapy (HAART) -- also called HIV/AIDS drug "cocktail" therapy -- is credited with lowering the rates of HIV-related disease and death in developed countries such as the U.S. HAART includes protease inhibitors as well as the older reverse-transcriptase inhibitors (for example, zidovudine, or AZT).

Resistance of HIV-1 -- the most common form of HIV in the U.S. and other developed countries -- to antiretroviral drugs is the main cause of HIV treatment failure. The primary causes of the development of drug-resistant HIV strains include 1) insufficient treatment to suppress the infection and 2) patient failure to follow the treatment regimen as directed.

Previous studies had calculated the rate of HIV resistance to zidovudine at 5-15%, but no previous studies had been done to calculate the rate of resistance to protease inhibitors.

"We analyzed 82 patients with primary HIV-1 in the Geneva area, from January 1996 to July 1998, and we found 10% of patients [had] mutations associated with resistance to reverse-transcriptase inhibitor [RTI] therapy," researcher Sabine Yerly, MSc, tells WebMD. "We thought we'd find some [resistance,] but we didn't expect to find such a high prevalence of transmission of resistance -- 10% is a very high percentage." Yerly is a research associate in the laboratory of senior researcher Luc Perrin, MD, at the Geneva University Hospital.

"What is also alarming for us is [that] we found 4% of patients with a resistance to protease inhibitors," says Yerly. "Protease inhibitors in Switzerland [became] available in 1995. These patients were infected between 1996 and 1998, and it means that in 2 years we [have seen] this resistance develop."

"I don't think this is terribly surprising; it is too bad, but it is something I think everybody anticipated might happen," Charles Carpenter, MD, tells WebMD. "I would guess that the likelihood of resistance is very similar in the big cities on the East Coast [of the U.S.] as it is in Geneva. Perrin is a first-rate investigator, and his lab is very good; I think the data are solid." Carpenter, a professor of medicine at Brown University, reviewed the study for WebMD.